I found this link that talks about both marital confidence and spousal testimonial privilege. It says that for the first, the spouse CAN prevent the other spouse from testifying about a marital confidence BUT the privilege generally survives the marriage.
For the second, the spouse called to testify can waive the privilege, but it's not generally applicable after the marriage.
Also, the second privilege only applies in criminal cases.
If that is a correct assessment, it seems like it doesn't really matter in this case, since the first privilege generally survives the divorce and the second can be waived at any time. You're right, it's a good question for the verified lawyers. I'd like to hear how this works in real life -- especially whether there's an exception to the general rule that marital confidences privilege surviving the divorce if there are pending felony charges. Hmm...
http://en.wikipedia.org/wiki/Spousal_privilege